The present invention relates to lamp sockets, and more particularly to a safety lamp socket which firmly holds down the lamp bulb in position when installed and, which prohibits direct contact of the fingers from the contact metal plates when the lamp bulb is removed.
Various decorative strings and Christmas tree light sets are well-known and intensively used everywhere in the world, more particularly in western countries during Christmas holidays. While using these decorative lighting devices, the requirement for a safety operation is critical. UL and CSA define strict specifications on these products.
The lamp socket for a decorative string or Christmas tree light set is generally comprised of an internally threaded plastic socket body, a plastic socket cap fastened to the socket body to hold down the electric wire, and two contact metal plates mounted within a respective hole on the socket body and disposed in contact with either conductor of the electric wire. When the lamp bulb is threaded into the socket body, the tip and ring contacts of the lamp bulb are respectively connected to the electric wire through the contact metal plates. This structure of lamp socket is functional however, it has drawbacks. One drawback of this structure of lamp socket is that the inner thread of the plastic socket body doesn't firmly match the ring contact of the lamp bulb, and the socket body may expand when hot, causing the lamp bulb disconnected from the socket body. Another drawback of this structure of lamp socket is that the contact metal plates may be touched by the fingers when the lamp bulb is removed, causing an electric shock.